1 A strange curate's egg

As Roberto Mancini fights to keep his job, how he would kill for the kind of "curate's egg" of a season Sir Alex Ferguson described in his pre-match notes. As an epitaph for the campaign in which Manchester United welcomed Mancini's all-but-dethroned champions 15 points ahead and on the brink of a 20th title "part bad, but with some great redeeming features" was a sly gem of a message from the Scot to the Italian. Despite a win that bolsters City's spirits, as the Abu Dhabi hierarchy ruminate on Mancini's future, a careful digestion of this line shows them precisely what they are up against on domestic turf even before the Champions League failures are considered.

2 What's eating Rooney?

Before this 165th Mancunian derby Wayne Rooney made the following statement: "If I was losing against my mates I could lose my cool if things went against me and now I am a pro that is the same. You need to be like that I think." Ferguson may argue that all major players need an edge but the way the striker clattered into James Milner on 31 minutes was beyond anything in the fiercely competitive file. This was a two-footed challenge that had Rooney leaving the ground as he recklessly cleaned out his England colleague. When Mike Dean produced his yellow card Rooney's angry reaction was reminiscent of those occasions when he can lose his rag – and the team his services – with the Liverpudlian lucky not to be shown red. This all pointed to the familiar frustration viewed whenever Rooney loses form and his way. Yet this onfield demeanour was strange: a glance at his numbers show the fine return of 16 goals in31 appearances for United.

3 City can head for Wembley in good spirits

A sweet left-foot strike in-off Phil Jones that swept past David de Gea was followed by a golf swing celebration and a punch of the air by Milner as he broke the deadlock after 51 minutes. Next up Carlos Tevez broke as City again pinned United back and the sense formed that, whatever else followed, – apart admittedly from, say, four unanswered home strikes – Mancini's men would head for Sunday's FA Cup semi-final against Chelsea in fine heart. After Vincent Kompany's unlucky own-goal levelled proceedings Rafael Benítez will note how City continue to fight as Sergio Agüero sent them into dreamland.

4 The need for width and pace

Top of the summer shopping list for the Blues will be one lightning wing, at least. On Monday night the nominal wide men were Samir Nasri and Milner with David Silva, who also usually lines up down the corridors, playing behind Tevez. Exhibit A to show why City cannot stretch teams enough in this area came when Nasri skipped down the left near United's 18-yard box. Instead of driving wide to beat the last defender on the outside before whipping in a cross the Frenchman cut inside and the move stuttered. Like Silva, Nasri is a playmaker who operates from the margins with each relying on the pace in his heads not legs. The same is true of Milner and, broadly, the rest of the squad: there was also the sight of Tevez being caught in a foot race by that renowned speedster Michael Carrick. Naming the fastest player in the City ranks is difficult with the answer including two defenders – Pablo Zabaleta and Kompany, and only one attacker, Agüero.

5 Can City catch United next season?

This was a snapshot of the sides' present state but in how his gang dealt with the champions-elect Mancini strengthened his argument that the 15-point margin is not a true reflection of the respective quality of the sides. City walked off at the break having made it three consecutive halves they had dominated on United's home turf, following the 6-1 rout here last season in a convincing, all-round display. They started the contest by forcing a first corner after Tevez, Silva, Nasri, Zabaleta and Milner all combined. Later Gareth Barry led a midfield that pressed higher up the park than City often have this season. And they continued to press as the match went on. But to challenge again next season will not only be about the recruitment in the close season. Mancini – or whoever is in charge – might wish to pin up what the former Ferguson lieutenant Gary Neville wrote before this game of their title triumph last season: "Was that City's mountain? Under Sir Alex United are never at the top of the mountain – there is no mountain, no end in sight. It's just a continuous, relentless charge year after year."